Various optical-based blood measurement devices, such as fingertip pulse oximetry devices, can measure some parameters of blood flow in a patient, such as heart rate and local oxygen saturation of hemoglobin. Other techniques can be employed for determination of regional saturation of hemoglobin, such as forehead-applied devices. These devices are non-invasive measurement devices, typically employing solid-state lighting elements, such as light-emitting diodes (LEDs) or solid state lasers, to introduce light into the tissue of a patient. The light is then detected and analyzed to determine the parameters of the blood flow in the patient.
However, conventional optical-based blood measurement devices typically are subject to patient-specific noise and inconsistencies which limits the accuracy of such devices. These patient-specific issues can include variations in tissue pigment, local blood flow or volume variations, vascular inhomogeneity of the tissue under measurement (i.e. a large vessel underneath device on tissue), tissue layer scattering, or tissue hydration, among others. Additionally, incorrect application of these devices can lead to incorrect determination of blood and tissue parameters due to optical shunting or undesired propagation of the optical signals through air gaps or blood-deficient tissue between optical emission and detection points.